feat: caclulate valid holidays for specified timerange

BREAKING CHANGE: The year is not a constructor argument for KHol anymore, it is now a function parameter

src/main/kotlin/org/javafreedom/khol/KHol.kt

@@ -5,9 +5,11 @@ import kotlinx.datetime.LocalDate
 /**
  * Some doc
  */
-class KHol(val holidays: HolidayDeclarations, val year: Int, val validIn: String) {
+class KHol(private val holidays: HolidayDeclarations, private val validIn: String) {
+
+    fun validHolidays(year: Int) : List<LocalDate> {
+        if (year < 1990) throw KHolException()
 
-    fun validHolidays() : List<LocalDate> {
         val result = mutableListOf<LocalDate>()
 
         holidays.declarations().filter {
@@ -19,4 +21,15 @@ class KHol(val holidays: HolidayDeclarations, val year: Int, val validIn: String
 
         return result
     }
+
+    fun validHolidays(start: LocalDate, end: LocalDate) : List<LocalDate> {
+        if (start >= end) throw KHolException()
+
+        val result = mutableListOf<LocalDate>()
+        for (year in start.year..end.year) {
+            validHolidays(year).filter { it > start && it <= end }.forEach { result.add(it) }
+        }
+
+        return result
+    }
 }

src/main/kotlin/org/javafreedom/khol/KHolException.kt

@@ -0,0 +1,4 @@
+package org.javafreedom.khol
+
+class KHolException: RuntimeException() {
+}

src/test/java/org/javafreedom/khol/KHolGermanHolidaysJavaTest.java

@@ -11,9 +11,9 @@ public class KHolGermanHolidaysJavaTest {
     @Test
     void testNW2024() {
         var holidayDeclarations = new GermanHolidayDeclarations();
-        var sut = new KHol(holidayDeclarations, 2024, "NW");
+        var sut = new KHol(holidayDeclarations, "NW");
 
-        var validHoldays = sut.validHolidays();
+        var validHoldays = sut.validHolidays(2024);
 
         assertEquals(11, validHoldays.size());
         assertTrue(validHoldays.stream().anyMatch(it ->

src/test/kotlin/org/javafreedom/khol/KHolGermanHolidaysTest.kt

@@ -2,6 +2,7 @@ package org.javafreedom.khol
 
 import kotlinx.datetime.LocalDate
 import org.javafreedom.khol.declarations.GermanHolidayDeclarations
+import org.junit.jupiter.api.assertThrows
 import kotlin.test.Test
 import kotlin.test.assertContains
 import kotlin.test.assertEquals
@@ -11,47 +12,45 @@ internal class KHolGermanHolidaysTest {
 
     @Test
     fun northrhineContainsReformationDay() {
-        val sut = KHol(GermanHolidayDeclarations(), 2024, "NW")
+        val sut = KHol(GermanHolidayDeclarations(), "NW")
 
-        val validHolidays = sut.validHolidays()
+        val validHolidays = sut.validHolidays(2024)
 
         assertEquals(11, validHolidays.size)
         assertContains(validHolidays, LocalDate.parse("2024-11-01"))
     }
 
     @Test
     fun hessenDoesNotContainReformationDay() {
-        val sut = KHol(GermanHolidayDeclarations(), 2024, "HE")
+        val sut = KHol(GermanHolidayDeclarations(), "HE")
 
-        val validHolidays = sut.validHolidays()
+        val validHolidays = sut.validHolidays(2024)
 
         assertEquals(10, validHolidays.size)
         assertFalse { validHolidays.contains(LocalDate.parse("2024-11-01")) }
     }
 
     @Test
     fun thereAreNoDefinedHolidaysBefore1990() {
-        val sut = KHol(GermanHolidayDeclarations(), 1989, "HE")
+        val sut = KHol(GermanHolidayDeclarations(), "HE")
 
-        val validHolidays = sut.validHolidays()
-
-        assertEquals(0, validHolidays.size)
+        assertThrows<KHolException> { sut.validHolidays(1989) }
     }
 
     @Test
     fun bremenHolidaysBefore2018WithoutReformationDay() {
-        val sut = KHol(GermanHolidayDeclarations(), 2017, "HB")
+        val sut = KHol(GermanHolidayDeclarations(), "HB")
 
-        val validHolidays = sut.validHolidays()
+        val validHolidays = sut.validHolidays(2017)
 
         assertEquals(9, validHolidays.size)
     }
 
     @Test
     fun bremenHolidays2018WithReformationDay() {
-        val sut = KHol(GermanHolidayDeclarations(), 2018, "HB")
+        val sut = KHol(GermanHolidayDeclarations(), "HB")
 
-        val validHolidays = sut.validHolidays()
+        val validHolidays = sut.validHolidays(2018)
 
         assertEquals(10, validHolidays.size)
     }